This invention relates generally to the treatment of intervertebral discs, and more particularly, to apparatus and methods for providing supplemental nutrition to intervertebral discs.
Intervertebral discs provide mobility and a cushion between the vertebrae. At the center of each disc is the nucleus pulposus which, in the adult human, is composed of cells and an insoluble extracellular matrix which is produced by the nucleus itself. The extracellular matrix is composed of collagen, proteoglycans, water, and noncollagenous proteins. The nucleus pulposus is surrounded by the annulus fibrosis, which is composed of cells (fibrocyte-like and chondrocyte-like), collagen fibers, and non-fibrillar extracellular matrix. The components of the annulus are arranged in 15-25 lamellae around the nucleus pulposus.
The cells of the nucleus pulposus have chondrocyte-like features. In an adult human, the cells of the nucleus pulposis obtain nutrients and eliminate waste by diffusion through blood vessels in the endplates of the vertebrae adjacent to the disc. Blood vessels do not course into the nucleus pulposis. The relative vascular isolation of the nucleus pulposis imparts isolation of nucleus pulposis cells from the body""s immune system.
To date, the treatment of degenerative disc disease has relied for the most part on eliminating the defective disc or disc function. This may be accomplished by fusing the vertebra on either side of the disc. In terms of replacement, most prior-art techniques use synthetic materials to replace the entire disc or a portion thereof. My pending U.S. patent application Ser. No. 09/415,382 discloses disc replacement methods and apparatus using synthetic materials.
Unfortunately, disc replacement using synthetic materials does not restore normal disc shape, physiology, or mechanical properties. Synthetic disc replacements tend to wear out, resulting in premature failure. The problems associated with the wear of prosthetic hip and knees are well known to those skilled in orthopedic surgery. The future of treating degenerative disc disease therefore lies in treatments which preserve disc function. If disc function could be restored with biologic replacement or augmentation, the risk of premature wearout would be minimized, if not eliminated.
However, some researchers believe the vertebral endplates of vertebrae involved in degenerative disc disease do not allow sufficient diffusion of nutrition to the disc cells. Diseased endplates could thus lead to death of the intradiscal cells. Accordingly, any technique capable of providing or augmenting the delivery of such nutrition would be welcomed by patients and the medical community.
This invention is directed to a method of treating an intervertebral disc by providing supplemental nutrition to increase viability and longevity. In the preferred embodiment, the invention uses one or more porous stents that function to irrigate the disc space. The stents provide channels for diffusion of fluids and nutrients from the vertebral endplates. The stents may extend across the vertebral endplates to facilitate the transfer of nutrients and oxygen from the vertebral bodies.